And now, a personal story this memorial day weekend. In the spring of 2004 I met an extraordinary group of soldiers in Iraq, involved in one of the most ferocious battles of the war, a platoon was ambushed, eight soldiers killed in a matter of hours and more than 60 wounded. At the time it was the largest loss of life for the 1st cavalry division since Vietnam. I have stayed in touch with many of those soldiers and their families through multiple deployments and multiple battle fields. But a few weeks ago, it was a different kind of meeting, a ten-year reunion at ft. Hood, Texas. A weekend about brotherhood and an unbreakable spirit. It was the day that would define them as a unit, as soldiers, as men. It's almost undescribable. It was probably the loudest thing I ever heard. The fire came from the right-hand side of the street, from the left. Reporter: Soldiers that had never been in battle. 19 pinned down in an alley. The rest of the battalion racing to rescue them. Unprotected, exposed, facing masses of armed insurgents. We see the Charlie company truck, rode down the road to us, four flat tires.÷ú engine on fire. Wounded. So many wounded, so many dead. Piles of bloody boots and body armor stacked outside the aide station. Inside a young army doctor, David Mathia, until that day, treated only the children of soldiers back home in Texas. I'm a pediatrician, it was shocking at first to see these battle wounds, the best word I could come up with is it was like a tidal wave. A tidal wave that would continue for 15 months until their end of the deployment. They lost 169 soldiers. Some guys have seen some things that no one ever wants to see. I understand now what it means when you go to a veterans' ceremony and you see the old veterans get together hug and cry. You didn't really understand it, I understand it now. Reporter: And ten years later, Gary understands it even better. And that's what this is all about. It's about a family -- not a unit, not a battle in a city. But a family. It seems like a lifetime ago. You walk in here and it feels like yesterday. Reporter: What do you remember most of that day? Just belief. I believe everything happens for a reason, right? You'll never be alone and that's just the way it is. It's a brothership. Reporter: A brothership, a family that has grown and struggled but survived. On this hot Texas night, they are, again, one. God, we come together as people who have been through the unthinkable. God, I just pray to those who are not here. I pray to their families that this will be a time of healing. Reporter: How old is he? 25. Reporter: Angel's younger brother was killed trying to rescue the platoon. His name like the others not etched on a granite memorial. It was where the soldiers gathered the second day. Ten years ago today, our hearts and lives changed forever. Not only for those who lost someone but for those who returned home with memories they never asked for. Reporter: Never asked for and for some -- almost too much to bear. What has it meant to you? It's huge. This is what I needed. I needed this to kind of turn the next page, if you will. Reporter: It's been hard doing that? Yeah. Yeah, it's been hard. Reporter: Eric and Justin know the pain as well. They were in that alley together. Under withering fire. Today, they are both fathers and students. Is it hard seeing the guys who aren't doing so well? It does hurt, because it's like our brothers. The guy you're looking at in did mirror he knows you're hurting. After after begghanistan, that's when I got to get help. Reporter: The young doctor, he practices medicine in Wisconsin, he and his wife just adopted a child from China. Adding to the five they already had. The pediatrician still thinks about that first night of trauma, a decade ago. You were broken up last night during your beautiful prayer, P what was going through your mind right then, what happened to you? Desperately wishing we could have brought everybody back. Reporter: Troy, you lost the first soldier on April 4th. He was your guy. I paid many respects to him and begged for forgiveness. Reporter: Why do you say beg for forgiveness? It's family, right? You lose part of your family. Reporter: And Gary, the wise and courageous young colonel, he is now a two-star general and headed off to command the 101st airborne. But no other division, no soldiers will ever take the place of these heroes. That bond is forever. And those families are heroic as well. The officer who was a division

This transcript has been automatically generated and may not be 100% accurate.

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